Osmotic systems manufactured in the form of osmotic devices for delivering a beneficial agent to an environment of use are known to the art in U.S. Pat. Nos. 3,845,770 and 3,916,899. The systems disclosed in these patents comprise a semipermeable wall that surrounds a compartment containing an agent. The wall is permeable to an external fluid, substantially impermeable to agent, and thee is a passageway through the wall for delivering the agent from the system. These systems release agent by fluid being imbibed through the wall into the compartment at a rate determined by the permeability of the wall and the osmotic pressure gradient across the wall to produce a solution of soluble agent, or a solution of an osmotic attractant containing insoluble agent which solution in either operation is dispensed from the system. These systems are extraordinarily effective for delivering both an agent that is soluble in the fluid and exhibits an osmotic pressure gradient across the wall against the fluid, and for delivering an agent that has limited solubility in the fluid and is admixed with an osmotically effective compound that is soluble in the fluid and exhibits an osmotic pressure gradient across the wall against the fluid. While the above systems are outstanding and represent a pioneer advancement in the delivery art, and while they are endowed with ideal delivery kinetics useful for delivering numerous beneficial agents at a controlled and continuous rate to environments of use, there is an occassional instance where the delivery kinetics of the system can be unexpectedly improved to lead to more desirable results. For example, the rate of agent delivered by the system is constant for most agents as long as excess solid agnt is present in the system with its rate declining parabolically towards zero as the agent's concentration decreases below saturation. That is, both the solubility and the density of the agent influence the amount of agent delivered at a constant rate, and that amount delivered at a declining rate is proportional to the solubility of the agent and inversely proportional to its density. These actions often make it difficult to utilize the full specific therapeutic effect of an agent, particularly when the agent is very soluble in the fluid and concomitantly a portion of the agent cannot be delivered at a constant rate over a prolonged period of time, and when the agent has limited solubility in the fluid. These latter agents do not readily form solutions or suspensions with the fluid and they exhibit limited osmotic pressure gradients across the wall, which properties make it difficult to dispense them for utilizing their full therapeutic effect. The prior art improved the delivery kinetics for both of these agents by mixing with the agents an osmagent that is coadministered with the agent. Additional prior art osmotic devices are seen in U.S. Pat. No. 3,760,804. This patent discloses a device having a rigid housing member formed of an impermeable material and having a movable separation therein forming two chambers. While this device operates successfully for its intended purpose, its use is limited because the agent must be in a semi-solid form, movable separators are hard to make and leaks often occur at the separation between the compartments. In U.S. Pat. No. 3,760,805, an osmotic device is disclosed consisting of a rigid housing member containing two bags. One bag is made of an impervious material housing a solution, semi-solid, gel or paste containing an agent, and the other bag is made of a permeable material housing an osmotic solute. While this device represents an advancement in the art, its use is limited because the agent must be in a liquid-like state. This precludes high agent loading because the liquid occupies space in the bag. Also, solid agents cannot be delivered from the device because the wall of the bag housing the agent is impermeable to the passage of fluid, which structural feature prevents both inhibition of fluid and mixing of the solid agent with fluid. The fluid is needed as a carrier for delivering agent in solution or suspension from the system. In U.S. Pat. No. 3,760,809 there is disclosed an osmotic device formed of two helical compartments consisting of one formed of an impermeable material separated by a sliding barrier plug from a second helical compartment. Also, U.S. Pat. No. 3,929,132 discloses an osmotic device made of a rigid housing member having a removable dispensing head, a threaded end, an internal agent chamber made with impermeable walls, an osmotic solute chamber having a porous membrane support for a semipermeable membrane, with the chambers separated by a movable barrier. The device of this patent operates in a manner similar to the device of U.S. Pat. No. 3,760,804 and has the same limitations. The present invention improves the delivery kinetics of the system and increases the amount of agent delivered therefrom by using an agent chamber formed with a semipermeable wall thereby making possible the housing of larger amounts, the mixing, and the delivery of solid agent from the system. The invention also uses the osmagent in a separate chamber for delivery of substantially pure agent from the system. A mathematical presentation pertaining to the instant subject matter is known in J. Pharm. Sci., Vol. 64, No. 12, pages 1987 to 1991, 1975.